TA/FC Dry sump pressure dropping

Thought I would bounce this off the keyboard experts here.

On my TA/FC I have a dry sump system which consists of a 22 quart tank (filled with 18 quarts), a Plueger dry sump pump, System One oil filter and the tank is vented to the upper right frame rail which takes it to the puke tank.

Typically we have 150-160 or so pounds of oil pressure at idle when it's cold and it drops the usual 15 to 20 when the oil gets hot. 70wt Valvoline Nitro oil. Durring the warm up in the pits, at stage RPM (6,000 to 6,500 RPM), it hangs around 130-135 pounds.

Last weekend at Pomona after the first session it developed an issue. At idle it was 145 or so. When Daniel took it up to stage RPM the oil pressure dropped to as low as 89 pounds. When he let it drop back to an idle it jumps back up to 145 pounds. We checked out the engine then changed the oil since it was about the 4th warm up on it with all the rain delays and fired it up again. At idle it was 145, it held steady at 100 pounds at stage RPM, then jumped back up to 145 pounds at idle. 100 pounds is still about 30-35 lower than our history of warm-ups.

We changed oil pumps and, again, it was 145 pounds at idle but it bumped up to 125 pounds at stage so we figured that would work. Once we were ready we were still delayed for the next two days. On Sunday evening before we headed to the staging lanes to race Clint Thompson in round one we fired it up and did a stage RPM computer dump. It was back down to 100 pounds at stage RPM. Once Daniel let off the throttle the oil pressure jumped back up to 145 pounds.

We disected both pumps and pump checks and they are fine. The bottom end of the engine looks fine. We changed the oil twice during the course of weekend after multiple warm ups getting ready to make several runs...which never happened. All the lines are new and there does not appear to be any air leaks.

Anyone else deal with this or have a heads up they can offer? I am going to remove the entire oil system this week and I'll check venting and everything else I can think of. We made plenty sure the oil was up to temperature before hitting stage RPM on any warm up.

RG

 

System One is on the pressure side of the pump. The pressure line feeds the filter so the oil passes through the outside of the screen to the center, then it feeds directly into the engine.

Except for connections the entire system in hard lined. The small sections of hose to connect the tubes are stainless wire reinforced.

 

Another possiblity is a restriction on the inlet side on the pump, maybe a blockage, blocked breather or collapsed hose as Mike said. I have seen this exact problem before in a wet sump engine with a partially blocked inlet screen.
Jim

 

I herd/saw this scenerio once,..found that the oil was not what
it should have been, we were running 70 wt and somehow what
came out of the 70wt marked jugs was actually 50 wt....
we did not carry any 50 wt, it was how it cam from the manufacturer
/ dealer who sold it to us

?????

Vic

 

two possibilities i can think off

1- is the 2-way valve from the oil tank to the frame rail/tank ok does it pass both ways- could be creating vacumn in the tank and not allowing the pump to pull oil into it?

2- how are you measuring oil pressure with just the transducer (bad?) from computer or do you have a gauge that confirms press drop also

 

We don't run a two way valve, and the guage matches the transducer numbers.

 

have you tried the stage RPM with out the screen in the filter??

 

I've been running the System One filter for a hundred years. I can't imagine that all of the sudden, on the 6th of February 2009, the filter decides to give us grief. However, believe it or not, we did put a new one in can just to make sure it wasn't collapsing. Plueger feels the filter acts as an anti-aeriator and likes to see it on the pressure side of the pump rather than filtering the oil as it heads to the dry sump tank.

Hmmm.

 

Randy, is there any possibility that the engine is losing a cam bearing. Saw this once before. Started out with erratic oil pressure when revved up at stage to low pressure at rpm. An internal bleeder of sorts. Of course the bottom end looks great. Just an idea to add to the great one's above. Just a little piece of silicon can start it off.

 

Did you change cylinder blocks? If so did the restrictor get left out?

 

It's not the same race car we ran at the finals thanks to Grant Downing and Chuck Worsham Racing.

The first warm up on Thursday it was fine. The only thing I changed was my mind about how much fun I was having hanging out at the races in the rain.

We monitored the dry sump tank oil level and found it to be nearly full when we shut it off seconds after hitting stage RPM so I know the pump wasn't high and dry.

As soon as I get over this flu I'm going to pull the thing apart and give everything a good look-see.

Daniel was sicker than a dog on Monday and was running a fever in the motorhome. At the end of the day we decided to pack it in. He hasn't been back to work yet.

RG

 

OK-OK.....Sounds like you guys passed the flu bug right into the oil system.

Or.....did you change the oil pressure sensing location. Or like Will suggested it could be related to the extremly high condensation conditions.

Hope you get to feeling better...............Blessings........Ron Clevenger.

 

Randy, from your description, and barring a vaccum leak on the supply side to the pump, my thought is that the cold temp/cold oil pops the pump's bypass open dropping the pressure at stage rpm but not enough to reseat the bypass. When the motor is back at idle the pressure drops enough to reseat the bypass and the pressure pops back up.
The only other possibility I see is just cold heavy oil causing the pump to cavitate when the speed goes up. You could test this with a lighter weight oil to see if the condition is the same. Jeff Johnsen

 

Jeff and Ron:

From what I hear we weren't the only team having this issue last weekend. Weather came to mind as that was the only thing that changed for the worse. We had low temps and very high humidity especially during the rain storms. Tuesday it dried out but we weren't there.

After swapping the spool in the barrell valve and adjusting for the conditions we were still having oil contamination issues (lots of alcohol) even though idle temps and temps at stage were where I like to see them. The contamination is why we weren't bashfull about changing the oil.

Randy